1. Field of the Invention
The present invention relates to a vibration eliminating apparatus for an apparatus such as a semiconductor manufacturing apparatus and an electron microscope, and particularly to a high precision vibration eliminating apparatus for shielding vibration from an installation floor and for controlling a vibration generating force produced by such an apparatus itself, which vibration and vibration generating force have adverse influences on the yield of a product and accuracy in measurement or observation.
2. Description of the Prior Art
A machine such as an electron microscope and a semiconductor manufacturing apparatus, which should be stable vibration, has been supported by a vibration eliminating apparatus. As an example of a conventional stably supported apparatus, a pneumatic spring or a vibration-proof rubber has been used. A machine such as an electron microscope and a semiconductor manufacturing apparatus has been mounted on a vibration eliminating floor board provided with pneumatic springs or vibration-proof rubber so that the vibration of an installation floor is absorbed by the pneumatic springs or the vibration-proof rubber to avoid the vibration of the floor from having any adverse influence on the yield of the product and the accuracy in measurement by shielding the vibration from the machine installed on the vibration eliminating floor board. However, since the vibration eliminating apparatuses using pneumatic springs or vibration-proof rubber are mechanical, it has been difficult for the vibration eliminating apparatus utilizing pneumatic springs and vibration-proof rubber to completely eliminate vibration, particularly small vibrations. Moreover, such a vibration eliminating apparatus cannot absorb large vibration exceeding the limit of the pneumatic spring and the vibration-proof rubber, and may sometimes have an impact on a machine such as the electron microscope, mounted on the floor board.
In addition, whether or not the vibration level (absolute value) is maintained within an allowable range as a result of the elimination of the vibration is not monitored. Consequently, if an apparatus operates when a vibration level exceeds an allowable range, an adverse influence is given to the yield of the product and the accuracy in measurement and observation.